问题现象：
#####immediate关闭数据库，重新开启归档,即可。
我在执行开启归档命令后报错误ORA-00265
SQL> alter database archivelog;
alter database archivelog
*
ERROR at line 1:
ORA-00265: instance recovery required, cannot set ARCHIVELOG mode
问题分析：
从如上错误我们可以看到是因为datafile，controlfile，redolog中的SCN号不一致导致无法开启归档，那么导致该问题的原因是因为我重启数据库到mount的时候采用的是startup force mount;因为这个命令实际上是做了两步操作，分别如下:
1、shutdown abort ---强制关闭数据库
2、startup mount
既然我们隐含的做了shutdown abort操作之后，也就意味着datafile，controlfile，redolog这里面的SCN号肯定不一致，需要在open数据库的过程中做recover，由于他们的SCN号不一致，所以会导致无法在mount状态下开启archivelog,如下:
SQL> startup mount force;
ORACLE instance started.
Total System Global Area 2505338880 bytes
Fixed Size 2255832 bytes
Variable Size 620758056 bytes
Database Buffers 1862270976 bytes
Redo Buffers 20054016 bytes
Database mounted.
SQL> alter database archivelog;
alter database archivelog
*
ERROR at line 1:
ORA-00265: instance recovery required, cannot set ARCHIVELOG mode
问题解决办法:
针对该问题，最简单的解决办法是，将数据库open，这个时候会进行recover操作，完成之后再进行shutdown immediate后启动到statup mount就可以开启归档了，详细见如下：
SQL> alter database open;
Database altered.
####recover日志信息如下
alter database open
Beginning crash recovery of 1 threads
parallel recovery started with 3 processes
Started redo scan
Completed redo scan
read 1522 KB redo, 175 data blocks need recovery
Started redo application at
Thread 1: logseq 7, block 10941
Recovery of Online Redo Log: Thread 1 Group 1 Seq 7 Reading mem 0
Mem# 0: /DBData/woo2/redo01.log
Completed redo application of 0.44MB
Completed crash recovery at
Thread 1: logseq 7, block 13985, scn 991198
175 data blocks read, 175 data blocks written, 1522 redo k-bytes read
Wed Sep 03 22:39:35 2014
Thread 1 advanced to log sequence 8 (thread open)
Thread 1 opened at log sequence 8
Current log# 2 seq# 8 mem# 0: /DBData/woo2/redo02.log
Successful open of redo thread 1
MTTR advisory is disabled because FAST_START_MTTR_TARGET is not set
Wed Sep 03 22:39:35 2014
SMON: enabling cache recovery
[13499] Successfully onlined Undo Tablespace 2.
Undo initialization finished serial:0 start:3565124 end:3565194 diff:70 (0 seconds)
Verifying file header compatibility for 11g tablespace encryption..
Verifying 11g file header compatibility for tablespace encryption completed
SMON: enabling tx recovery
Database Characterset is AL32UTF8
No Resource Manager plan active
replication_dependency_tracking turned off (no async multimaster replication found)
Starting background process QMNC
Wed Sep 03 22:39:36 2014
QMNC started with pid=23, OS id=16119
Completed: alter database open
Wed Sep 03 22:39:37 2014
db_recovery_file_dest_size of 4182 MB is 0.00% used. This is a
user-specified limit on the amount of space that will be used by this
database for recovery-related files, and does not reflect the amount of
space available in the underlying filesystem or ASM diskgroup.
Wed Sep 03 22:39:37 2014
Starting background process CJQ0
Wed Sep 03 22:39:37 2014
CJQ0 started with pid=24, OS id=16134
Starting background process SMCO
Wed Sep 03 22:39:43 2014
SMCO started with pid=30, OS id=16149
#####immediate关闭数据库，重新开启归档,即可。
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 2505338880 bytes
Fixed Size 2255832 bytes
Variable Size 620758056 bytes
Database Buffers 1862270976 bytes
Redo Buffers 20054016 bytes
Database mounted.
SQL> alter database archivelog;
Database altered.
SQL> alter database open;
Database altered.
SQL>
###打开归档alert日志信息如下
ALTER DATABASE MOUNT
Successful mount of redo thread 1, with mount id 3606990310
Database mounted in Exclusive Mode
Lost write protection disabled
Completed: ALTER DATABASE MOUNT
Wed Sep 03 22:45:06 2014
alter database archivelog
Completed: alter database archivelog
alter database open
Wed Sep 03 22:45:12 2014
LGWR: STARTING ARCH PROCESSES
Wed Sep 03 22:45:12 2014
ARC0 started with pid=20, OS id=16867
ARC0: Archival started
LGWR: STARTING ARCH PROCESSES COMPLETE
ARC0: STARTING ARCH PROCESSES
Wed Sep 03 22:45:13 2014
ARC1 started with pid=21, OS id=16871
Wed Sep 03 22:45:13 2014
ARC2 started with pid=22, OS id=16873
Wed Sep 03 22:45:13 2014
ARC3 started with pid=23, OS id=16875
ARC1: Archival started
ARC2: Archival started
ARC1: Becoming the \
